The present invention relates to an image processing apparatus and method capable of adding information on image data.
There are many cases (such as prevention of forgery) in which additional information should be added to basic image data and which however the added information is imperceptible to human eyes. Conventionally, when additional information is added and multiplexed to image data of an original, the original image data is considerably deteriorated. To solve the above problem, U.S. Pat. No. 5,257,119, which utilizes the visual characteristic of human eyes, adds the additional information to an yellow component of an original multi-color image. The added information will be imperceptible due to the characteristic.
However, there are cases in which the added information is needed to be extracted or restored. In order to be able to extract and decode the added information from an output image generated by the conventional techniques, additional data with a considerably large value needs to be added and modulated in the multiplexing processing. The modulation will deteriorates the image quality, while it will provide the advantage that the added information is imperceptible with human eyes.
Since the conventional technique utilizes a particular color which is difficult to discriminate with human eyes, the multiplexing process is practically applied only to a multi-color image, but not to a monochromatic image.
Furthermore, in the case where the information adding processing is applied to a multi-color image and then the output image is post-processed with such color conversion process, the added information is converted to a color which is of high perceptibility. Thus, it becomes unpractical.
Furthermore, the added information is easily read by a third person, and this is inconvenient when the added information is confidential.
Still further, there are additional image pattern which cannot be added and/or separated in the conventional techniques. Thus, it is impossible to provide a stable multiplexing or addition.